ScalarField: optimize computeMinAndMax

Also properly clears min and max if the field is not empty, but all
points are invalid.

include/ScalarField.h

@@ -103,31 +103,36 @@ namespace CCCoreLib
 
 	inline void ScalarField::computeMinAndMax()
 	{
-		if (!empty())
+		ScalarType minVal, maxVal;
+
+		bool minMaxInitialized = false;
+		for (std::size_t i = 0; i < size(); ++i)
 		{
-			bool minMaxInitialized = false;
-			for (std::size_t i = 0; i < size(); ++i)
+			const ScalarType& val = at(i);
+			if (ValidValue(val))
 			{
-				const ScalarType& val = at(i);
-				if (ValidValue(val))
+				if (minMaxInitialized)
+				{
+					if (val < minVal)
+						minVal = val;
+					else if (val > maxVal)
+						maxVal = val;
+				}
+				else
 				{
-					if (minMaxInitialized)
-					{
-						if (val < m_minVal)
-							m_minVal = val;
-						else if (val > m_maxVal)
-							m_maxVal = val;
-					}
-					else
-					{
-						//first valid value is used to init min and max
-						m_minVal = m_maxVal = val;
-						minMaxInitialized = true;
-					}
+					//first valid value is used to init min and max
+					minVal = maxVal = val;
+					minMaxInitialized = true;
 				}
 			}
 		}
-		else //particular case: no value
+
+		if (minMaxInitialized)
+		{
+			m_minVal = minVal;
+			m_maxVal = maxVal;
+		}
+		else //particular case: zero valid values
 		{
 			m_minVal = m_maxVal = 0;
 		}